This application is based on Application No. 11-66860 filed in Japan on Mar. 12, 1999, Application No. 11-223281 filed in Japan on Aug. 6, 1999, and Application No. 11-296041 filed in Japan on Oct. 19, 1999, the contents of which are incorporated hereinto by reference.
The present invention relates to a battery unit in which a plural number of cells are connected in series or in parallel, and especially to a battery unit which can detect an abnormal temperature rise of at least one of a large number of cells constituting a battery unit for use in an electric car.
Battery units which are provided with temperature sensors such as PTC elements for detecting an abnormal temperature rise of a cell so as to prevent deterioration, heating trouble and the like of the cell from occurring are widely known.
Further, electric power devices for driving an electric car motor have been proposed, each of which contains a large number of cells electrically connected in series and can provide high voltage and high current. Also, electric power devices for use in electric cars, each of which is provided with temperature sensors, are known. Such an electric power device has been disclosed, for example, in Japanese Non-examined Patent Publication No. 270094/1998.
In the electric power device disclosed in the Publication, a temperature sensor is adhered to each of the cells constituting a battery unit, and an abnormal temperature rise is detected by measuring a total electric resistance of the temperature sensors.
However, the electric power device disclosed in this Publication requires the same number of temperature sensors as that of the cells constituting the device, since a temperature sensor is adhered to each of the cells. An electric power device for use in an electric car demanding high output and high voltage contains an extremely large number of cells, and therefore, it requires an extremely large number of temperature sensors.
As a result, such a device has a disadvantage that since its parts and assembling processes such as connecting processes of the temperature sensors increase in number, its manufacturing cost becomes high.
Therefore, a first object of the present invention is to provide a battery unit which comprises a large number of connected cells and can detect an abnormal temperature rise of a cell with a reduced number of temperature sensors adhered to the cells.
As shown in FIG. 1, the abnormal temperature rise detecting device disclosed in the Publication No. 270094/1998 has a PTC sensor 10 adhered to the outside of each of the cells constituting a battery unit, and all of the adhered PTC sensors 10 are connected in series to a resistance measuring device to measure total resistance of the PTC sensors. When at least one of the cells to which PTC sensors are adhered, respectively, receives an abnormal temperature rise, a resistance of a PTC sensor 10 adhered to the cell increases extremely, and the resistance measuring device detects the abnormality.
However, in the abnormal temperature rise detecting device disclosed in this Publication, all of the PTC sensors 10 adhered, respectively, to the cells are connected in series and total resistance of the connected PTC sensors 10 is measured to detect abnormal temperature rise. Here, each PTC sensor 10 has its inherent difference i.e. dispersion of temperature characteristic. Therefore, as the number of the connected PTC sensors increases, such dispersions of the PTC sensors 10 are summed up, and all of the dispersions of the PTC sensors 10 are added to the measured value of total resistance. Especially, as described in the Publication No. 270094/1998, when a temperature sensor is adhered to each of 126 or 252 cells constituting a battery source device for use in an electric car and total resistance of the temperature sensors is measured, the measured value contains an extremely large total of dispersions.
Consequently, if a cell receives an abnormal temperature rise and a resistance value of a PTC sensor adhered to the cell increases extremely, sometimes the increased resistance value cannot be detected since each PTC sensor has a dispersion as mentioned above. In addition, when these dispersions are taken into account and a threshold value for detecting an increase of resistance value is set as a high value including the dispersion value, the abnormal temperature rise cannot be detected until the resistance value rises above the threshold value, and there is a problem in that the detection of abnormal temperature rise takes a lot of time.
Further, in an abnormal temperature rise detecting device disclosed in the Publication, since all of PTC sensors adhered respectively to 126 cells are connected in series, it is impossible to detect which one of the 126 cells receives the abnormal temperature rise. Therefore, treatments such as mending and exchange of the cells and the device must be carried out over a wide range. Thus, this device has a disadvantage that maintenance, inspection and the like thereof cannot be rapidly achieved.
Therefore, a second object of the present invention is to provide a battery unit having an abnormal temperature rise detecting device which can precisely detect an abnormal temperature rise of a cell without being influenced by a dispersion of temperature characteristic of each temperature sensor, can rapidity detect a resistance value increase caused by an abnormal temperature rise to reduce detecting time, and can detect an abnormal temperature rise of a cell in rather a small range even if the device is used in an electric power device comprising a plural number of cells, so that treatment for the abnormality, maintenance and inspection of the device and the like can be rapidly carried out.
A battery unit according to the present invention comprises a large number of cells connected in series or in parallel. Temperature sensors for detecting cell temperature are respectively adhered to cells constituting the battery unit. One temperature sensor is adhered to one cell, but temperature sensors are not adhered to all of the cells. In a battery unit having this structure, a lower number of temperature sensors than that of a number of connected cells are provided, and cells adjacently provided with temperature sensors, respectively, and cells not provided with temperature sensors are mixedly connected. The temperature sensors are a PTC sensors or a thermistors.
Each of the cells not provided with any temperature sensor may be provided with a heat collecting member for collecting a temperature of the cell and transferring temperature data of the cell to a temperature sensor. In this battery unit, a cell provided with a temperature sensor and a cell provided with a heat collecting member are connected adjacent to each other. A temperature sensor is preferably disposed at a position on the surface of a cell near the adjacent cell provided with a heat collecting member.
A main material of the heat collecting member is one selected from the group consisting of iron, nickel, copper, aluminum and an alloy containing one of these metals.
Further, the battery unit comprises a plural number of cells each provided with a temperature sensor and cells each provided with a heat collecting member, wherein the temperature sensors adhered to the cells can be electrically connected in series to one another through the heat collecting members.
In the battery unit mentioned above, each of the cells provided with a heat collecting member is preferably disposed between the cells provided with a temperature sensor. Further, in the battery unit mentioned above, a temperature sensor may be disposed between two adjacent cells and heat collecting members may be respectively provided on the cells on both sides of the temperature sensor. In such a battery unit, since a heat collecting member is provided on the surface of a cell and connected to a temperature sensor, cell temperature is collected by the heat collecting member and transferred to the temperature sensor. Thereby, the heat collecting member can detect abnormal temperature rise of a cell. As a result, by connecting a lower number, not the same number, of temperature sensors than a number of the cells constituting the battery unit, the abnormal temperature rise of all of the cells can be detected.
Consequently, the battery unit can reduce the number of temperature sensors and thereby, assembling processes and parts of the battery unit can be reduced in number, so that manufacturing cost thereof can be lowered.
Further, according to the present invention, since temperature sensors are divided into small blocks and a control unit detects abnormality of each of the small blocks, abnormality can be detected in a rather small range of the small block with a lower number of temperature sensors than the number of cells connected in the battery unit.
Further, a battery unit according to the present invention is provided with a plural number of cells and an abnormal temperature rise detecting device comprising temperature sensors adhered respectively to the cells, a resistance of each temperature sensor changing during a temperature rise, and an abnormal temperature rise detecting circuit for measuring a resistance value of the temperature sensors and detecting abnormal temperature rise of a cell. The temperature sensors are divided into a plural number of temperature sensor blocks. In each sensor block, a same number of temperature sensors are connected in series. On the other hand, the abnormal temperature rise detecting circuit detects abnormal temperature rise by comparing resistance values of the temperature sensor blocks with each other.
In a battery unit having this structure, a plural number of temperature sensors are divided into temperature sensor blocks, and resistance values of the temperature sensors are respectively measured. When a difference between the resistance values becomes above a predetermined value, an abnormality of a cell is detected.
According to the present invention, since resistance values of the temperature sensor blocks are compared with one another, differences i.e. dispersions of temperature characteristic of the temperature sensors can be offset. Therefore, when any one of the cells receives an abnormal temperature rise and resistance value of a PTC sensor adhered to the cell increases extremely, only the increased value can be precisely detected. As a result, the abnormality can be detected precisely and without errors, free from the influence of dispersions of temperature sensors such as PTC sensors.
In addition, since dispersions of temperature sensors are off set, it is not necessary to set a set value of difference between resistance values of temperature sensors for detecting abnormal cell temperature to be unnecessarily large. Thereby, the abnormal temperature rise detecting device can sensitively react to an increase of resistance value, and the detecting time can be shortened.
In addition, since the temperature sensors such as PTC sensors are divided into temperature sensor blocks, if an abnormal temperature rise is caused in any one of a large number of cells, the detection can be carried out in every temperature sensor block and thereby, treatment such as mending or exchange can be achieved in a rather narrow range to speed up the maintenance inspection and the like.
As a result, a battery unit having this structure can precisely and rapidly detect an abnormal temperature rise of a cell when it is used as a battery source which comprises an extremely large number of connected cells for an electric car or a hybrid type car. Further, the battery unit is safe and is easily maintained and inspected, so that it can be easily treated as a battery source for an electric car and the like.
The above and further objects and features of the present invention will more apparent from the following detailed description with accompanying drawings.